Semiconductor storage devices such as a NAND flash memory have been downscaled to increase storage capacity. Development of memories using new materials is progressing to achieve further downscaling. Novel memories such as a resistance random access memory (ReRAM), a phase-change RAM (PRAM), a phase-change memory (PCM), an interfacial PCM (iPCM), a ferroelectric NAND-type memory (FeNAND), and a magnetic random access memory (MRAM) are developed.
Among these novel memories, the PCM and the iPCM are brought to a low resistance state (a Set state) or a high resistance state (a Reset state) according to phase transition of a phase-change film of the relevant memory cell. This enables the PCM and the iPCM to store therein logical data.
In such a resistance-change memory, data is written to a memory cell by supplying a current and a voltage to the memory cell. Therefore, the distance (the length of interconnection) from a read/write circuit on the current supply side or a source line driver on the current sink side to a memory cell affects the voltage applied to the memory cell. For example, when a bit line from the read/write circuit to a memory cell or a source line from the memory cell to the source line driver (a current sink) is relatively short, a voltage drop or a voltage increase (voltage floating) caused by interconnection is small. Accordingly, a sufficiently-large write voltage difference can be applied to the memory cell. On the other hand, when a bit line from the read/write circuit to a memory cell and a source line from the memory cell to the source line driver (the current sink) is long, a voltage drop or a voltage increase caused by interconnection becomes large. Accordingly, a voltage difference applied to the memory cell becomes relatively small. In this case, there is a risk that data cannot be written to the memory cell.
As described above, in the conventional resistance-change memory, there are cases where a sufficiently-large write voltage cannot be applied to a memory cell depending on the position of the memory cell in a memory cell array.